WASHINGTON - An "all clear" was issued at Joint Base Andrews after reports of an active shooter originated from a caller who misidentified security forces performing routine inspections.

The incident began around 9 a.m. Thursday when an initial report was made. It centered around the Malcolm Grow medical facility on base where personnel were directed to shelter in place and first responders were called.

To add to the confusion, the report of the active shooter was made at the same time the base was preparing to conduct an active shooter exercise. "Reports of a real-world active shooter situation at the medical facility were miscommunicated before the exercise was able to begin," the base said in a statement. "There was a misidentification of the security forces emergency services team who were conducting a routine inspection of the medical facility, which caused the distress call to the base defense operations center."

During the lockdown, which lasted about 90 minutes, armed military personnel were seen directing traffic outside of the gates of the facility. Several people were led out of the base during this time and some vehicles were turned away. Vice President Joe Biden, who was scheduled to leave from Andrews on Thursday morning, had his trip delayed by the lockdown.

The "all clear" was given around 10:40 a.m. "Fortunately, this was not a life-threatening situation," said Col. Brad Hoagland, 11th Wing and JBA commander in a statement posted online. "We take all threats seriously and reacted to ensure the security of those on the base. I applaud the quick reaction of our first responders in keeping the safety of our JBA family a number one priority. In addition, we thank our local authorities for quickly standing by and offering their assistance.”